Terrifying, blood stained note found on terrorist's body

Never before seen footage has revealed how four men accused of being part of a terror plot were under intense police ground and aerial surveillance in the hours leading up to the murder of NSW Police employee Curtis Cheng.

On Monday, surveillance footage played to the Downing Centre Local Court revealed how police were following, watching, listening and recording the movements of the men and the moment they allegedly sourced the gun which was used to kill Mr Cheng on October 2, 2015.

The footage was played during a committal hearing for three accused terrorists Talal Alameddine, 24, Milad Atai, 21 and Mustafa Dirani, 23 - all of whom were wearing prison greens as they watched from the dock.

The trio are facing a number of charges including preparing and planning a terrorist act.

CCTV footage played to the court also showed 15-year-old killer Farhad Jabar raise his finger in an Islamic State salute to a camera within the Parramatta Mosque shortly before he executed Mr Cheng outside NSW Police headquarters on Charles Street at Parramatta.

It is the Crown case the accused men plotted to supply the 15-year-old with the gun which was used to execute Mr Cheng.

The court was also shown a bloody note which was found on Jabar's body after the murder of Mr Cheng which he had rewritten to "disbelievers".

"By the will of Allah I have come today to put terror in your hearts," the note read.

Crown prosecutor Paul McGuire SC said the prosecution case was the group were caught on phone taps discussing how to obtain the gun on the day of Mr Cheng's murder.

The court was played a conversation between Alameddine and Raban Alou, another man accused of plotting the terror attack but his charges are not subject of the current committal hearing.

"What did you bring?" Alou asks Alameddine as the pair drive in a car towards Merrylands in Sydney's west.

Alameddine: Well I brang (sic) the 30 cal bro. You wanted to get the big one?

Alou: nah nah nah Parramatta shit bro "wallah"

Alameddine: This is bad man.

Mr McGuire told the court it was the Crown case that the conversation between Alameddine and Alou was a discussion about the acquisition of a .30 calibre firearm.

He told the court the recorded conversation showed Alou was unhappy about the type of firearm that had been acquired which prompted the group to drive to Merrylands to get another weapon.

Earlier during the committal hearing the court was shown a series of Whatsapp messages between Alou, Atai and Dirani where they share pictures of Australian Defence Force personnel who appear to be getting off a bus.

At one point in the Whatsapp conversation Alou says in relation to the images: "May allah curse them all and destroy them to pieces".

The hearing is being held to see whether magistrate Clare Farnan thinks there is sufficient evidence for the matter to proceed to a trial before a jury.